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Terms in this set (34)
TF-Metallic corrosion in potable water is always the result of an electro chemical reaction
TF-For corrosion to occur both an electric current and a chemical reaction must occur
TF-A noble metal is a metal that does not corrode easily and is more scarce and more valuable than base metals
TF-The effect of a high concentration of carbonate and bicarbonate in water (high alkalinity) is that the water has a strong tendency to resist a change in pH
Oxygen plays an important role in corrosion both at the anode and at the cathode
TF-Phosphate and silicate compounds are frequently added at the water treatment works as a corrosion control method
TF-Use of either form of lime to control corrosion will add hardness to the water
TF-The best measure of the corrosivity of soil is the soil resistivity
TF-Laboratories need extra certification to test for lead and copper
TF-Corrosion control treatment often involves adjusting pH and alkalinity to make water less corrosive
What is tuberculation?
The development or formation of a small mound of corrosion products (rust) on the inside of iron pipe
What is an electro chemical reaction?
A Chemical reaction where the flow of electric current itself is an essential part of the reaction
What is a cathode?
The point where electric current leaves the metal and flows to the anode through the electrolyte
What is a base metal?
A metal such as iron that reacts with dilute hydrochloric acid to form hydrogen
What is a dielectric coupling?
An insulator or non-conducting substance used to separate copper and steel to prevent corrosion
What is erosion corrosion?
The erosion of copper pipes during very high water velocities
What does the loss of dissolved oxygen in a water distribution system indicate?
The water contains oxidizable organic matter or gross corrosion is occurring
Where in the water treatment process should corrosion reduction chemicals be added?
Why should water samples tested for corrosiveness be taken after postchlorination?
Because the chlorine may react with the chemicals used to reduce corrosivity
Why should zinc phosphate compounds not be used to control corrosion caused by water that will be stored in an open reservoir?
Because the phosphate may cause algal blooms
What is cathodic protection?
A process used to reduce or inhibit corrosion of metal exposed to water or soil
How can internal pipe corrosion be controlled?
By treating the water to achieve calcium carbonate saturation
What is a first draw sample?
The first Liter of water collected from a tap that has not been used for at least 6 hours
What is corrosion?
The gradual decomposition or destruction of a material by chemical action often due to an electrochemical reaction
What is an anode?
A point from which metal is lost and electric current begins
Which biological factors influence corrosion?
sulfate reducing bacteria
What are the adverse impacts of sulfate reducing bacteria in water?
Free hydrogen sulfide can react with water forming sulfuric acid, which is extremely corrosive to metals,
sulfide may be released as gaseous hydrogen sulfide, generating the characteristic rotten egg odor,
sulfide may react with metals, producing black metal sulfide deposits on the inside of pipes and fixtures
Which toxic heavy metals are significant sources of contamination of drinking water?
Why must caustic soda be handled with great care?
It dissolves human skin,
it produces heat when mixed with water,
it reacts with amphoteric metals (such as aluminum) generating hydrogen gas, which is flammable and may explode if ignited
Which chemicals may be used in corrosion control programs?
The application of cathodic protection requires consideration of which factors affecting a corrosion problem?
Dissimilar metals to be protected,
soil and water characteristics,
soil moisture content,
straight currents already present in the ground or water
Which parts of the body can be damaged by lead?
red blood cells
What are the health effects of copper?
stomach and intestinal distress
Which items are corrosion related water quality indicators?
corrosion inhibitor concentration,
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